Compressional wave sender and receiver



May 10,1938. w. KUNZE 2,116,522

- COMPRESSIQNAL WAVE SENDER ANb RECEIVER Filed Dec. 5, 1935 5:41 wry ATTORNEY.

Patented May 10, 1938 UNITED STATES 2,110,522 7 comasssromr. WAVE SENDER AND nnonrvaa Willy Kunze, Bremen, Germany, assignor to Submarine Signal OompanaBoston, Masa, a corporation of Maine Application December 5. 1933, Serial No. 701,012 In Germany January'l, 1933 '1 Claims. (01. 177-386) The present invention relates to apparatus for the production and reception of compressional waves, especially high-frequency waves. It has particular application to the production and reception of high-frequency compressional waves in a liquid medium such as water.

i In the present invention use is made of the magnetostrictive properties of certain metals and alloys. Magnetostrictive oscillators, as devices of 10 this type are conveniently called, have been made in the past but have not been of great value on account of their small energy output. This was "in part due to the losses which occur in this type of device. It has been proposed, in order to keep "the losses-low, to build up the magnetostrictive vibratory body from sheet rings or laminations.

A pile of such laminations is assembled with thin layers of insulating material between them and the whole pressed together so that a unitary body of definite natural frequency results.

These arrangements have the great disadvantage that at the high frequencies for which such apparatus is mostly employed large frictional losses are set up within the body of laminations. 5 It appears that this was due to the fact that an absolutely rigid union of the individual laminae could not be assured.

, An object pf the present invention is to s'et forth a magnetostrictive vibratory body in which 30 there is no looseness between the individual members which may give rise to undesirable frictional losses.

This is accomplished according to the present invention by employing a multiplicity of mag- 35 netostrictive members of equal length, for example, Wires, thin rods, sheet strips, thin-walled tubes or the like. These may advantageously be mounted parallel to 'each other without metallic contact between them, their ends being rigidly 40 joined together in some manner so that a single' unitary longitudinally vibrating body results whose natural frequency can be made use of. The joining of the ends of the individual magnetostrictive members may be made. either by 45 means of insulating material or by means of one or two metallic end masses. material is used for this purpose, it may be applied in a liquid state or by means of suitable adhesive or the individual members may be pressed 50 under pressure into the insulating material. A particularly useful construction is obtained when the ends of the individual members are rigidly joined to metallic masses as, for example, by soldering, brazing or welding.

55 Another feature of the invention consists in the magnetostrictive elements.

When insulating constructing the vibratory body of the oscillator in such a manner that a diflerent amplitude is obtained at the radiating member than the amplitude of the magnetostrictive member. This may be accomplished by employing masses, of 5 different magnitudes at the opposite ends of These masses are then connected by elastic members, namely the whole or a portion of the magnetostrictive elements. In such a structure the ends of the mag- 10 netostrictive elements having the largest mass will vibrate with the smallmt amplitude.

. It is a known principle that a radiating surface will radiate in' substantially a single direction only if its dimensions are large compared to the 16 wavelength of the energy being sent out or receivcd. This principle may be effectively em;- ployed according to the present invention by mounting upon a radiating plate a multiplicity of magnetostrictive elements covering substantially 20 the whole surface of the plate. Alternatively a number of magnetostrictive vibratory bodies, each composed of a plurality of magnetostrictive elements disposed parallel to but out of contact with each other and rigidly joined together at one or both ends, may be constructed. A plurality of such vibratory bodies may then be mounted upon a radiating plate of large dimensions compared to the wave length. If desired two such radiating plates may be employed, one at each end of the vibratory bodies. A directive efiect may also be obtained by mounting the radiating surface or surfaces of the magnetostrictive oscillator at the focus of a parabolic reflector.

The invention may be further understood by reference to the accompanying drawing in which Fig. 1 indicates schematically the construction of a vibratory body according to the present invention; Fig. 2 is a cross section through the magnetostrictive elements along the line II-II of Fig. 1; Fig. 3' shows a cross section similar to Fig. 2 but in which the magnetostrictive elements are in the form of sheet strips rather than rods or tubes; Fig. 4 is a section through a complete high-frequency sender or receiver; and Fig. 5 shows an alternative construction of a high-frequency sender or receiver and particularly one which has two radiating surfaces.

In the modification shown in Fig. l a plurality of magnetostrictive elements in the form of wires, rods or tubes l are arranged parallel to each other without metallic contact with each other. They are spaced from each other by means of two insulating discs 2 provided with suitable holes through which the magnetostrictive elements are passed. The individual elements I can easily be made with exactly the same length so that each has, accordingly, the same tuning as all the others.

- ments. When alternating current of the proper frequency corresponding to the frequency of the vibratory structure is passed through the coil 1, the individual magnetostrictive elements and thereby the entire vibratory structure will be set into vibration. A greater effect can be obtained by also providing the coil 1 with a direct current which produces an initial magnetization.

By the above construction a vibratory structure is obtained which vibrates as a whole using a definite natural frequency. On the other hand, on account of the rigid connection of the individual magnetostrictive elements with the end masses and by the elimination of insulating material between the individual elements, the losses are reduced to a minimum.

Fig. 2 shows a cross section through the magnetostrictive elements shown in Fig. 1 and demonstrates the manner in which substantially the whole inner surface of the radiating member 4 is provided with magnetostrictive elements. The

spacing between the individual elements is made as small as possible consistent with convenient mechanical construction and yet large enough to insure complete electrical and mechanical insulation between the individual elements. By using a multiplicity of magnetostrictive elements covering substantially the whole surface of the radiating mass 4, vibration of the latter as a whole is assured and no bending or diaphragm action takes place. In order to reduce electrical losses in the end masses 3 and 4, these may be slotted or they may be made of a special material of high electrical resistance.

Fig. 3 shows a cross section taken in a similar manner as that ofFig. 2 but of a somewhat different contruction. In this case the magnetostrictive elements are in the form of sheet strips I which are arranged radially about the longitudinal' axis of the vibratory structure. In a manner'similar to that shown in Fig. 2 two insulating discs may be provided having radial slits through which the magnetostrictive strips are passed whereby the spacing of the strips from each other is assured. Alternatively the strips may be mounted in radial slots cut in the end masses 3 and 4 to which they are rigidly joined by soldering, brazing or welding or by means of a hardened insulating material or the like. The arrangement of the magnetostrictive elements need not, of course, as in Figs. 2 and 3, be in a circular form, but they may be arranged in any desired configuration to suit the purpose for which the oscillator is to be used.

Fig. 4 shows a soundsender or receiver in which a 'magnetostrictive vibratory body 8 composed of a multiplicity of magnetostrictive elements is joined to an end mass 9 which is, in turn, fixed to a metal plate I of relatively very large mass.

At the ends of these magnetostrictive. elements there are arranged two metallic masses The mass 8 may be fixed to the plate ill by means of screw threads 35. The other end mass ll transfers the vibratory energy to and from the surrounding medium, for example, water. A coil l2 surrounds the vibratory elements 3.

A cylindrical casing i3 is provided surrounding the whole structure and closed at one end by the plate Ill to which it is secured by means of the screws 26 and made watertight by a gasket II.

The outer surface of the radiating member II is covered by a membrane I which may be made of thin metal pressed against the member I I and the casing I! by means of the clamping ring l1 and the screws 31. It has also been found advantageous to fix the membrane l8 rigidly to the member II as by means of soldering, brazing or welding. The coil I2 is connected through'conductors ll to a source of alternating and direct current when the oscillator is used for producing sound waves or with an amplifier when used as a receiver. When alternating current is passed through the coil 2 the end mass II is set into energetic vibrations which are transferred to the water as compressional wave energy. On the other hand, if compressional-wave energy strikes the membrane l6 which forms a part of the mass I I, the vibrations are transferred to the magnetostrictive elements I and produce an alternating current in the coil i2 which may be amplified and listened to by means of a telephone receiver, or ii' the frequency is above the audible range, the alternating currents produced in the coil l2 may be made audible by a heterodyne amplifier or other known means.

It should be noted that it is important to provide as small a space as possible between the housing l3 and the piston end mass II in order to prevent any diaphragm action in the membrane I which is used only for the purpose of making the inside of the oscillator watertight. Instead of using the metallic membrane l5 other material may be used, or the membrane may be omitted entirely and the space between the casing l3 and the end mass ll may be filled with some material such as rubber which is impervious to the water.

In the modification shown in Fig. 5 magnetostrictive elements I! are provided with end masses 2!! and 2! designed to vibrate as pistons. The vibratory structure so resulting is supported at a vibratory node by means of a plate 24 of insulating material. If the end members 20 and 2| are of equal mass, the node will be at the center of the elements IS. The plate 24 is secured in a casing formed of two parts 22 and 23 clamped together by means of the bolts 30 made watertight by means of rubber gaskets 3| and 22. The piston radiating members 20 and 2| project through the casing 22 and 23 and have their ends .formed in the shape of a truncated cone. The

space between the members 20 and 2| and the casing is made watertight by means of the rubber rings 33 and 34. Excitation of the magnetostrictive elements is provided by the coils 25 and 26. These may be connected in series and supplied with alternating and direct current, or one coil may be used for the direct polarization current while the other coil is used for the alternating current.

A further feature of the device shown in Fig. 5

is the provision of means for completing the mag-" netic circuit. This consists of a yoke 21 which completely surrounds the coils 25 and 28. The air gaps 29 and 30 between the yoke and the members 20 and 2| are made as small possible tion perpendicular to the radiating surface, that is the dimensions of the radiating surface must be large compared to the wave length of the frequency employed. In order to keep the diameter of the radiating surface within reasonable limits it is preferable to choose the natural frequency of the oscillator in the vicinity of or above the audible limit. The excitation of the oscillator may be provided by alternating current produced by a motor-generator or a vacuum-tube oscillator and may be controlled by a key.

It has also been found useful to employ an impulse excitation produced by unidirectional current impulses from the discharge of a condenser or by means of the damped vibrations of an oscillatory circuit having a spark gap Having now described my invention, I claim:

1. Apparatus for producing and receiving highfrequency compressional waves in water comprising a casing having an opening at one end, a mass positioned in said opening and substantially filling the same, means supporting said mass in said position comprising a thin web supporting said mass, means clamping said web at the end of the casing, a great number of magnetostrictive rods substantially covering one surface of said mass, a coil surrounding said rods and means supporting said coil within said casing.

2. Apparatus for producing and receiving highfrequency compressional waves in water comprising a casing having an opening, a mass of substantially rigid material positioned in said opening and filling the same, means freely supporting said mass in said opening to allow motion normal to the surface of the mass, a great number of magnetostrictive rods, means mounting said rods in said mass at the inside of said casing, said rods substantially covering the entire surface of the mass and a coil surrounding said rods f energizing the same.

3. Apparatus for producing and receiving highfrequency compressional waves in water comprising a casing having an opening at one end, a mass substantially filling said opening, means freely supporting said mass for motion transverse to its external surface comprising a thin web supporting said mass and means clamping said web at the end of said casing, a great number of magnetostrictive rods mounted at the end of the mass within the casing and covering substantially the entire surface of said mass insulating means spacing said rods and securing them in position with reference to each other, means including in part said casing of magnetic material and said rods and forming a completely closed magnetic circuit through said rods and casing wall and a coil surrounding said rods for energizing the same. 4. Apparatus for producing and receiving high frequency compressional waves in water comprising a cylindrical casing, means providing'a' heavy mass at one end of said casing and closing the same, a plate, a plurality of magnetostriction rods mounted in said plate and positioned normally thereof and substantially covering the whole plate, a mass mountedat the other end of said rods, means attaching said plate to the n'rass at the end of the casing, the rods running longitudinally thereof and the second mass being positioned in the opening at the end of the casing, means providing a web contacting said second mass and closing the end of the casing and a coil surrounding said rods positioned within the casing for energizing the same.

5. Apparatus for producing and receiving high frequency compressional waves in water comprising a cylindrical casing having an opening at one end, an assembly of parallel magnetostrictive rods closely spaced together but free from each other, a mass positioned at each end of the rods and means mounting the rods in said masses, said rods covering substantially the entire surface of said masses, a coil surrounding said rods and completing the magnetic circuit for the rods about the casing, means for attaching said assembly at one end of the casing and means covering the other end thereof for acoustically transmitting the vibrations to the propagating medium.

6. Apparatus for producing and receiving'high frequency compressionaiwaves in water comprising a cylindrical casing, an assembly of magnetostrictive rods arranged parallel but close to one another, a mass positioned at each end of the rods in which the rods are mounted, said rods covering substantially the entire surface of said mass, means for fixing the assembly at the back of the casing, a cover fixed to the front end of the casing and contacting said second mass, said rods being arranged parallel to the axis of said casing and a coil positioned within said casing pleting the magnetic circuit about the coil.-

7. Apparatus for producing and receiving high frequency compressional waves in water comprising a cylindrical casing having an opening at one end, a mass substantially filling said opening and means providing a thin web for attaching said mass to said casing, a great number of parallel magnetostrictive rods embedded in said mass normal to the external surface thereof, said rods being spaced free from one another but substantially so close together that no morethan another rod of the same diameter could be inserted between any two rods, a coil surrounding the whole group of rods and means completing the magnetic circuit for the magnetic field produced by the coil including said rods and the outer casing. 

